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Biomedical subjects

J H Jones

Publications and source records attributed to J H Jones.

At least 19 recordsLinked to original sources
PubMed2001

Frequency of and risk factors for epistaxis associated with exercise-induced pulmonary hemorrhage in horses: 251,609 race starts (1992-1997).

OBJECTIVE: To determine the frequency of epistaxis during or after racing among racehorses and identify factors associated with development of epistaxis. DESIGN: Retrospective study. SAMPLE POPULATION: 247,564 Thoroughbred and 4,045 Anglo-Arab race starts. PROCEDURE: Race start information (breed, age, sex, racing distance, and race type) was obtained for Thoroughbred and Anglo-Arab horses racing in Japan Racing Association-sanctioned races between 1992 and 1997. All horses that raced were examined by a veterinarian within 30 minutes of the conclusion of the race; any horse that had blood at the nostrils was examined with an endoscope. If blood was observed in the trachea, epistaxis related to exercise-induced pulmonary hemorrhage (EIPH) was diagnosed. RESULTS: Epistaxis related to EIPH was identified following 369 race starts (0.15%). Frequency of EIPH-related epistaxis was significantly associated with race type, age, distance, and sex. Epistaxis was more common following steeplechase races than following flat races, in older horses than in horses that were 2 years old, following races < or =1,600 m long than following races between 1,601 and 2,000 m long, and in females than in sexually intact males. For horses that had an episode of epistaxis, the recurrence rate was 4.64%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that frequency of EIPH-related epistaxis in racehorses is associated with the horse's age and sex, the type of race, and the distance raced. The higher frequency in shorter races suggests that higher intensity exercise of shorter duration may increase the probability of EIPH.

Age Factors↗
PubMed2000

Induction of Ca-independent PLA(2) and conservation of plasmalogen polyunsaturated fatty acids in diabetic heart.

Diabetes-induced changes in phospholipase A(2) (PLA(2)) activity have been measured in several tissues but are undefined in diabetic myocardium. We measured ventricular PLA(2) activity in control, streptozotocin-induced diabetic, and insulin-treated diabetic rats and characterized myocardial phospholipids to determine whether diabetes altered myocardial phospholipid metabolism. Increased membrane-associated Ca(2+)-independent PLA(2) (iPLA(2)) activity was observed in diabetes that was selective for arachidonylated phospholipids. Increased iPLA(2) activity was accompanied by an increase in choline lysophospholipids. Diabetes was associated with marked alterations in the phospholipid composition of the myocardium, characterized by decreases in esterified arachidonic and docosahexaenoic acids and increases in linoleic acid. The decrease in polyunsaturated fatty acids was confined to diacylphospholipids, whereas the relative amount of these fatty acids in plasmalogens was increased. Diabetes-induced changes in PLA(2) activity, lysophospholipid production, and alterations in phospholipid composition were all reversed by insulin treatment of diabetic animals. Diabetes-induced changes in membrane phospholipid content and phospholipid hydrolysis may contribute to some of the alterations in myocardial function that are observed in diabetic patients.

Animals↗
PubMed2000

Use of sevoflurane for anesthetic management of horses during thoracotomy.

OBJECTIVE: To evaluate sevoflurane as an inhalation anesthetic for thoracotomy in horses. ANIMALS: 18 horses between 2 and 15 years old. PROCEDURE: 4 horses were used to develop surgical techniques and were euthanatized at the end of the procedure. The remaining 14 horses were selected, because they had an episode of bleeding from their lungs during strenuous exercise. General anesthesia was induced with xylazine (1.0 mg/kg of body weight, IV) followed by ketamine (2.0 mg/kg, IV). Anesthesia was maintained with sevoflurane in oxygen delivered via a circle anesthetic breathing circuit. Ventilation was controlled to maintain PaCO2 at approximately 45 mm Hg. Neuromuscular blocking drugs (succinylcholine or atracurium) were administered to eliminate spontaneous breathing efforts and to facilitate surgery. Cardiovascular performance was monitored and supported as indicated. RESULTS: 2 of the 14 horses not euthanatized died as a result of ventricular fibrillation. Mean (+/- SD) duration of anesthesia was 304.9 +/- 64.1 minutes for horses that survived and 216.7 +/- 85.5 minutes for horses that were euthanatized or died. Our subjective opinion was that sevoflurane afforded good control of anesthetic depth during induction, maintenance, and recovery. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of sevoflurane together with neuromuscular blocking drugs provides stable and easily controllable anesthetic management of horses for elective thoracotomy and cardiac manipulation.

Anesthesia, General↗
PubMed1999

Im-trityl protection of histidine.

A rational attempt to prepare FmocHis(piTrt)OH regiospecifically gave in fact the well-known tau-trityl isomer, and experiments with model systems indicate that the prospects for access to pi-trityl histidine derivatives, which would be of great value for the racemization-free synthesis of histidine-containing peptides, are poor.

Histidine↗
PubMed1999

Neodymium: YAG transconjunctival laser revision of late-failing filtering blebs.

OBJECTIVE: To study the effectiveness of neodymium:YAG (Nd:YAG) laser transconjunctival revision of late-failing filtering blebs. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: Thirty consecutive patients from a glaucoma referral practice at the Ohio State University Department of Ophthalmology. INTERVENTION: Transconjunctival Nd:YAG laser revision of blebs diagnosed as failing secondary to episcleral fibrosis. MAIN OUTCOME MEASURE: Reduction in intraocular pressure (IOP) and survival of bleb. RESULTS: Reduction in IOP was attained in 24 (80%) of 30 patients with a mean prelaser IOP of 21.21 mmHg and a mean 1-week postlaser IOP of 13.97 mmHg (P < 0.0001). These results were maintained at the 1-, 3-, and 12-month follow-up visits with mean IOPs of 16.31 mmHg (P = 0.0008), 14.81 mmHg (P < 0.0001), and 15.25 mmHg (P = 0.0003), respectively. Two-year data were available on a small number of patients (4) with a mean of 15.25 mmHg (P = 0.0085). Mean time interval between trabeculectomy and laser revision was 31 months. CONCLUSION: Late-failing filtering blebs are often amenable to Nd:YAG transconjunctival revision.

Aged↗
PubMed1999

Is ventilation during maximal exercise limited by dynamic airway closure?

A study was undertaken to find if the reason why horses hypoventilate when running is that they experience expiratory flow limitation due to dynamic airway closure. To test this hypothesis, we measured peak expiratory flows on a Thoroughbred galloping on a treadmill and hypoventilating and compared those flows with the peak dynamically-limited flow that the same horse could achieve during a forced expiratory flow-volume manoeuvre. At the approximate lung volumes at which the horse was ventilating while running, it did not appear to be mechanically limited and appeared to have reserve capacity available potentially to increase its expiratory flow.

Animals↗
PubMed1999

Changes in left ventricular dynamics during graded exercise.

Three mature Thoroughbred horses were prepared surgically with ultrasonic sonomicrometer crystals affixed to their ventricular pericardia. Signals from crystals recorded dimensions of axes across the left ventricle. Cubic algorithms were fitted to dimensional data to generate volume estimates that matched stroke volumes simultaneously measured using the Fick principle. As horses stood at rest or exercised at various intensities (approx 7, 12, 24, 47 and 100% maximal rate of O2 consumption VO2max[), left ventricular dimensions were recorded and 20 consecutive diastolic and systolic volumes calculated. Although Fick estimates detected no difference in stroke volume at different exercise intensities, sonomicrometer measurements of stroke volume were significantly lower at rest and higher at VO2max. These differences mirrored changes in end-diastolic volume, although end-systolic volume did not change. At all exercise intensities, stroke volume was most variable and end-diastolic volume the least. The pattern conforms to the Frank-Starling mechanism, and indicates that at high exercise intensities ventricular myocytes generate high pressures with higher myocardial wall stress due to the increased size of the chamber.

Animals↗
PubMed1999

Cardiac output measurements using sonomicrometer crystals on the left ventricle at rest and exercise.

Eight horses were fitted surgically with 8 ultrasonic sonomicrometer crystals each attached to their left ventricular pericardia and a left atrial catheter. Three horses returned to treadmill performance with a maximum rate of oxygen consumption similar to their presurgical values. These horses were evaluated to determine how well sonomicrometer estimates of cardiac output agreed with those obtained by a steady-state method, the Fick principle. Variance between the 2 was similar to the coefficient of variation (approximately 12.5%) of the Fick estimates. We conclude that left ventricular sonomicrometer measurements in horses appear to give a reasonable estimate of ventricular dimensions and can, therefore, be used potentially to evaluate such variables as diastolic flow.

Animals↗
PubMed1999

Effects of frusemide on electrolyte and acid-base balance during exercise.

This study was undertaken to evaluate the effects of frusemide on the concentration of plasma electrolytes and the relationship between changes in electrolyte concentration and the simultaneous changes in acid-base balance in arterial and venous blood during intense exercise. Five exercise-conditioned Thoroughbred horses were exercised on a high-speed treadmill at a slope of 10% at speeds known to exceed VO2max. Horses participated in 3 randomised exercise trials in which they received either placebo (control), low-dose frusemide (0.5 mg/kg bwt), or high-dose frusemide (1.0 mg/kg) 4 h prior to exercise. Arterial and mixed venous blood samples were drawn before, during and after intense exercise. Packed cell volume (PCV), plasma protein, plasma electrolyte, plasma lactate concentrations and acid-base balance were determined. Frusemide at both dosages induced a significant metabolic alkalosis associated with a decrease in plasma çhloride[ in both arterial and mixed venous blood. There was a highly significant correlation between the strong ion difference (SID) and bicarbonate[ in all blood samples. The effects of frusemide on electrolyte concentration and acid-base balance were largely due to changes in SID.

Acid-Base Equilibrium↗
PubMed1999

Swimming overuse injuries.

Swimming injuries are unique in that they involve upper limb overuse more than lower limbs and that swimming is performed in a non-weight-bearing fluid setting. Identifying the mechanism of injury and prescribing appropriate management is not easy unless one has a thorough understanding of proper technique of the four competitive strokes. Understanding the psychology of swimming athletes will improve outcome and compliance. The goals of this article are to familiarize the reader with the diagnosis and management of swimming injuries and to improve the physician's effectiveness in dealing with swimmers through a thorough understanding of technique and psychology.

Athletic Injuries↗
PubMed1998

Optimization of the mammalian respiratory system: symmorphosis versus single species adaptation.

Taylor and Weibel's principle of symmorphosis hypothesized optimal design of the mammalian respiratory system, with no excess structure relative to its maximal O2 flux, VO2max. Although they found symmorphosis not to be a general principle of design, it might apply to a highly adapted aerobic athlete, e.g. the Thoroughbred racehorse. Using a mathematical model based on empirical data of the equine O2 transport system at normoxic VO2max, the fraction of the total limitation to O2 flux contributed by each of the respiratory transport steps is calculated as either the fractional change (F) in VO2max for a 1% change in each component, or as the fraction of total O2 pressure drop (R(int)) across each component at VO2max. When calculated as F, alveolar ventilation (VA) and pulmonary diffusing capacity (DLO2) are major limiting factors, circulatory convection (Q) is nearly as limiting, and peripheral tissue diffusing capacity (DTO2) is only one-third as important. When calculated as R(int), DLO2 is the major factor, VA and DTO2 contribute significantly, and Q is smallest. These patterns contrast with analogous studies in humans, in which Q is the single major limiting factor. The results suggest that strong selection for aerobic power in horses has maximized the malleable components of their respiratory systems until the least malleable structure, the lungs, has become a major limitation to O2 flux. Symmorphosis cannot determine if such a design is or is not optimized, as every system falls on a continuous distribution of relative optimization among species. However, the concept of symmorphosis is useful for establishing a framework within which a single species can be compared with a quantitatively defined hypothesis of optimal animal design, and compared with other species according to those criteria.

Adaptation, Biological↗
PubMed1997

Gradient elution reversed-phase chromatographic isolation of individual glycerophospholipid molecular species.

We describe a gradient elution reversed-phase high-performance liquid chromatographic approach for isolation of individual glycerophospholipid molecular species which greatly improves resolution and reduces run time compared to isocratic techniques. Separations were optimized and elution order and retention time data established by synthesizing 37 different homogeneous phospholipids comprising the major alkylacyl, diacyl and plasmalogen molecular species in samples derived from mammalian sources. Empirical equations which predict the elution order of individual species were derived. The method was validated with the use of complex mixtures of choline and ethanolamine glycerophospholipid species from isolated rabbit cardiomyocytes and porcine endothelial cells.

Animals↗
PubMed1996

Structural determinants of maximal O2 transport in muscles of exercising foxes.

The arctic blue fox (Alopex lagopus) has a specific maximal oxygen consumption (VO2 max/Mb = 3.6 ml O2.s-1.kg-1) that is approximately 1.6-fold greater than those of dogs and horses. The fox has one of the highest body mass specific skeletal muscle mitochondrial volumes (V(mt,m)/Mb = 44 cm3.kg-1) among mammalian athletic species matching its higher VO2 max/Mb. The structural components related to capillaries, such as specific capillary length density (J(c)/Mb = 348 km.kg-1) and specific capillary volume (V(c)/Mb = 4.8 ml.kg-1), are not greater in the fox than in the larger athletes. Because a greater specific muscle diffusing capacity for oxygen (DTO2/Mb) is not utilized by the fox to achieve a higher VO2 max/Mb, a higher pressure difference for diffusion in the muscle capillaries is the alternative explanation for the fox's higher VO2 max/Mb. This mechanism is suggested by the fox's higher arterial and mixed venous capillary PO2 (120 mm Hg and 37 mm Hg, respectively) and its shorter mean muscle capillary transit time for blood (tc = 0.28 sec) compared to larger species.

Animals↗